The long range purpose of this investigation is the elucidation of the mechanism of action of template directed polynucleotide polymerases in terms of their molecular structure. We shall seek to establish those features which may be shared by DNA dependent RNA polymerases (pro and eucaryotic), DNA dependent DNA polymerases (viral) and RNA dependent DNA polymerase (viral reverse transcriptase.) We shall employ as a model system E. Coli DNA dependent RNA polymerase. We propose to examine the following: a) the manner in which subunits are organized in the RNA polymerase molecule. b) the manner by which the enzyme binds to DNA template and the role of such subunits in forming the binding site and in modulating binding. The use of a DNA'ase modified DNA as a "psuedotemplate" will be examined. c) the topology of the active site; the spatial relationships between initiation, elongation and template binding subsites. d) the properties of the binding sites for antibiotics such as rifampcin and its derivatives and streptolydigin on RNA polymerase. Spectroscopic techniques will be extensively employed using absorption and emission properties of the aromatic amino acids in the enzyme, as well as those of "reporter" groups introduced at specific side chains in the enzyme molecule. Intramolecular distances between key regions of the enzyme molecule will be determined in energy transfer experiments with enzyme labeled with two different "reporter" groups.